Microchip Technology MCP4725EV Data Sheet

© 2009 Microchip Technology Inc.

DS22039D-page 23

When the device is connected to the I

2

C bus line, the

device is working as a slave device. The Master (MCU)
can write/read the DAC input register or EEPROM
using the I

2

C interface command. The MCP4725

device address contains four fixed bits ( 1100 = device
code) and three address bits (A2, A1, A0). The A2 and
A1 bits are hard-wired during manufacturing, and A0 bit
is determined by the logic state of A0 pin. The A0 pin
can be connected to V

DD

 or V

SS

, or actively driven by

digital logic levels.
The following sections describe the communication
protocol to send or read the data code and write/read
the EEPROM using the I

2

C interface. See Section 7.0

The write commands are used to load the configuration
bits and DAC input code to the DAC register, or to write
to the EEPROM of the device. The write command
types are defined by using three write command type
bits (C2, C1, C0). 

 shows the write command

types and their functions. There are three command
types for the MCP4725. The four “reserved” commands
in 

 are for future use. The MCP4725 ignores

the “reserved” commands. Write command protocol
examples are shown in 

. 

The input data code is coded as shown in 

The MSB of the data is always transmitted first and the
format is unipolar binary.

6.1.1

WRITE COMMAND FOR FAST 
MODE (C2 = 0, C1 = 0, C0 = X, 
X = DON’T CARE)

The fast write command is used to update the DAC
register. The data in the EEPROM of the device is not
affected by this command. This command updates
Power-Down mode selection bits (PD1 and PD0) and
12 bits of the DAC input code in the DAC register.

 shows an example of the fast write

command for the MCP4725 device. 

6.1.2

WRITE COMMAND FOR DAC INPUT 
REGISTER (C2 = 0, C1 = 1, C0 = 0)

In MCP4725, this command performs the same
function as the Fast Mode command in Section 6.1.1
“Write Command for Fast mode (C2 = 0, C1 = 0,
C0 = X, X = Don’t Care)”. 

command protocol for the MCP4725. 
As shown in 

, the D11 - D0 bits in the third

and fourth bytes are DAC input data. The last 4 bits (X,
X, X, X) in the fourth byte are don’t care bits. 
The device executes the Master’s write command after
receiving the last byte (4th byte). The Master can send
a STOP bit to terminate the current sequence, or send
a Repeated START bit followed by an address byte. If
the device receives three data bytes continuously after
the 4th byte, it updates from the 2nd to the 4th data
bytes with the last three input data bytes.
The contents of the register are updated at the end of
the 4th byte. The device ignores any partially received
data bytes if the I

2

C communication with the Master

ends before completing the 4th byte.

6.1.3

WRITE COMMAND FOR DAC INPUT 
REGISTER AND EEPROM                      
(C2 = 0, C1 = 1, C0 = 1)

When the device receives this command, it (a) loads
the configuration and data bits to the DAC register, and
(b) also writes the EEPROM. When the device is
writing the EEPROM, the RDY/BSY bit goes low and
stays low until the EEPROM write operation is
completed. The state of the RDY/BSY bit can be
monitored by a read command. 

 shows the

details of the this write command protocol and

 shows the details of the read command. 

111111111111 

(FFFh)

V

DD

 - 1 LSB

111111111110 

(FFEh) V

DD

 - 2 LSB

000000000010 

(002h)

2 LSB

000000000001 

(001h)

1 LSB

000000000000 

(000h)

0